ftrace: Synchronize the initialization of ftrace_opsgrafted

There's some internal state that ftrace_ops needs to have set, but since
it can be declared outside of the ftrace.c code, it calls
ftrace_ops_init() on the ops in every global function. The issue is that
if two tasks call it on the same ops at the same time it is possible to
have the initialization of one corrupt the initialization of the other
call.

Create a ops_mutex to use to synchronize every initialization of the
ftrace_ops. The mutex is taken within checking the ftrace_ops flag that
states it was initializied but the flag is checked again after the mutex
has been taken. Checking first outside the mutex allows it to shortcut
having to take the mutex. But then the check needs to be done again after
the mute is taken in case of races.

Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/20260902095501.6b59af20@gandalf.local.home
Fixes: f04f24fb7e48d ("ftrace, kprobes: Fix a deadlock on ftrace_regex_lock")
Reported-by: sashiko-bot@kernel.org
Close: https://lore.kernel.org/all/20260829025528.49A831F000E9@smtp.kernel.org/
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

1 files changed, 142 insertions, 0 deletions

diff --git a/drivers/hid/hid-vivaldi-common.c b/drivers/hid/hid-vivaldi-common.c
new file mode 100644
index 000000000..b12bb5cc0
--- /dev/null
+++ b/drivers/hid/hid-vivaldi-common.c
@@ -0,0 +1,142 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Helpers for ChromeOS HID Vivaldi keyboards
+ *
+ * Copyright (C) 2022 Google, Inc
+ */
+
+#include <linux/export.h>
+#include <linux/hid.h>
+#include <linux/input/vivaldi-fmap.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/types.h>
+
+#include "hid-vivaldi-common.h"
+
+#define MIN_FN_ROW_KEY 1
+#define MAX_FN_ROW_KEY VIVALDI_MAX_FUNCTION_ROW_KEYS
+#define HID_VD_FN_ROW_PHYSMAP 0x00000001
+#define HID_USAGE_FN_ROW_PHYSMAP (HID_UP_GOOGLEVENDOR | HID_VD_FN_ROW_PHYSMAP)
+
+/**
+ * vivaldi_feature_mapping - Fill out vivaldi keymap data exposed via HID
+ * @hdev: HID device to parse
+ * @field: HID field to parse
+ * @usage: HID usage to parse
+ *
+ * Note: this function assumes that driver data attached to @hdev contains an
+ * instance of &struct vivaldi_data at the very beginning.
+ */
+void vivaldi_feature_mapping(struct hid_device *hdev,
+			     struct hid_field *field, struct hid_usage *usage)
+{
+	struct vivaldi_data *data = hid_get_drvdata(hdev);
+	struct hid_report *report = field->report;
+	u8 *report_data, *buf;
+	u32 report_len;
+	unsigned int fn_key;
+	int ret;
+
+	if (field->logical != HID_USAGE_FN_ROW_PHYSMAP ||
+	    (usage->hid & HID_USAGE_PAGE) != HID_UP_ORDINAL)
+		return;
+
+	fn_key = usage->hid & HID_USAGE;
+	if (fn_key < MIN_FN_ROW_KEY || fn_key > MAX_FN_ROW_KEY)
+		return;
+
+	if (fn_key > data->num_function_row_keys)
+		data->num_function_row_keys = fn_key;
+
+	report_data = buf = hid_alloc_report_buf(report, GFP_KERNEL);
+	if (!report_data)
+		return;
+
+	report_len = hid_report_len(report);
+	if (!report->id) {
+		/*
+		 * hid_hw_raw_request() will stuff report ID (which will be 0)
+		 * into the first byte of the buffer even for unnumbered
+		 * reports, so we need to account for this to avoid getting
+		 * -EOVERFLOW in return.
+		 * Note that hid_alloc_report_buf() adds 7 bytes to the size
+		 * so we can safely say that we have space for an extra byte.
+		 */
+		report_len++;
+	}
+
+	ret = hid_hw_raw_request(hdev, report->id, report_data,
+				 report_len, HID_FEATURE_REPORT,
+				 HID_REQ_GET_REPORT);
+	if (ret < 0) {
+		dev_warn(&hdev->dev, "failed to fetch feature %d\n",
+			 field->report->id);
+		goto out;
+	}
+
+	if (!report->id) {
+		/*
+		 * Undo the damage from hid_hw_raw_request() for unnumbered
+		 * reports.
+		 */
+		report_data++;
+		report_len--;
+	}
+
+	ret = hid_report_raw_event(hdev, HID_FEATURE_REPORT, report_data,
+				   report_len, report_len, 0);
+	if (ret) {
+		dev_warn(&hdev->dev, "failed to report feature %d\n",
+			 field->report->id);
+		goto out;
+	}
+
+	data->function_row_physmap[fn_key - MIN_FN_ROW_KEY] =
+		field->value[usage->usage_index];
+
+out:
+	kfree(buf);
+}
+EXPORT_SYMBOL_GPL(vivaldi_feature_mapping);
+
+static ssize_t function_row_physmap_show(struct device *dev,
+					 struct device_attribute *attr,
+					 char *buf)
+{
+	struct hid_device *hdev = to_hid_device(dev);
+	struct vivaldi_data *data = hid_get_drvdata(hdev);
+
+	return vivaldi_function_row_physmap_show(data, buf);
+}
+
+static DEVICE_ATTR_RO(function_row_physmap);
+static struct attribute *vivaldi_sysfs_attrs[] = {
+	&dev_attr_function_row_physmap.attr,
+	NULL
+};
+
+static umode_t vivaldi_is_visible(struct kobject *kobj, struct attribute *attr,
+				  int n)
+{
+	struct hid_device *hdev = to_hid_device(kobj_to_dev(kobj));
+	struct vivaldi_data *data = hid_get_drvdata(hdev);
+
+	if (!data->num_function_row_keys)
+		return 0;
+	return attr->mode;
+}
+
+static const struct attribute_group vivaldi_attribute_group = {
+	.attrs = vivaldi_sysfs_attrs,
+	.is_visible = vivaldi_is_visible,
+};
+
+const struct attribute_group *vivaldi_attribute_groups[] = {
+	&vivaldi_attribute_group,
+	NULL,
+};
+EXPORT_SYMBOL_GPL(vivaldi_attribute_groups);
+
+MODULE_DESCRIPTION("Helpers for ChromeOS HID Vivaldi keyboards");
+MODULE_LICENSE("GPL");